    1   /*
    2    * Licensed to the Apache Software Foundation (ASF) under one or more
    3    * contributor license agreements.  See the NOTICE file distributed with
    4    * this work for additional information regarding copyright ownership.
    5    * The ASF licenses this file to You under the Apache License, Version 2.0
    6    * (the "License"); you may not use this file except in compliance with
    7    * the License.  You may obtain a copy of the License at
    8    *
    9    *      http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   * Unless required by applicable law or agreed to in writing, software
    12   * distributed under the License is distributed on an "AS IS" BASIS,
    13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   * See the License for the specific language governing permissions and
    15   * limitations under the License.
    16   */
    17
    18  package org.apache.log4j.util;
    19
    20  /**
    21   * This class switches MDC values into the order
    22   * (unreasonably) expected by the witness files.
    23   */
    24  public class MDCOrderFilter implements Filter {
    25
    26      /**
    27       * Unexpected orders of keys.
    28       * Note expected values are "va-one-one" and "va-one-two".
    29       */
    30    private static final String[] patterns =
    31            new String[] {
    32                    "{key2,va12}{key1,va11}",
    33                    "{key2,value2}{key1,value1}"
    34            };
    35
    36      /**
    37       * Replacement values.
    38       */
    39    private static final String[] replacements =
    40              new String[] {
    41                      "{key1,va11}{key2,va12}",
    42                      "{key1,value1}{key2,value2}"
    43              };
    44
    45    /**
    46     *  Switch order of MDC keys when not in expected order.
    47     */
    48    public String filter(final String in) {
    49      if (in == null) {
    50        return null;
    51      }
    52
    53      for(int i = 0; i < patterns.length; i++) {
    54          int ipos = in.indexOf(patterns[i]);
    55          if (ipos >= 1) {
    56              return in.substring(0, ipos)
    57                      + replacements[i]
    58                      + in.substring(ipos + patterns[i].length());
    59          }
    60      }
    61      return in;
    62    }
    63  }